“Zoroaster, the primeval institutor of sun-worship, cannot be called the founder of the dualistic system; neither was he the first to teach the unity of God, for he taught but what he had learned himself with the Brahmans. And that Zarathustra and his followers, the Zoroastrians, “had been settled in India before they immigrated into Persia”, is also proved by Max Muller. That the Zoroastrians and their ancestors started from India”, he says, “during the Vaidik period, can be proved as distinctly as that the inhabitants of Massilia started from Greece. Many of the gods of the Zoroastrians come out…as mere reflections and deflections of the primitive and authentic gods of the Veda.”
If now, we can prove – and we can do so on the evidence of the Kabala and the oldest traditions of the wisdom-religion, the philosophy of the old sanctuaries – that all these gods, whether of the Zoroastrians or of the Veda, are but so many personated occult powers of nature, the faithful servants of the adepts of secret wisdom – Magic – we are on secure ground.
Thus, whether we say that Kabalism and Gnosticism proceeded from Masdeanism or Zoroastrianism, it is all the same, unless we meant the exoteric worship – which we do not. Likewise, and in this sense, we may echo King, the author of the Gnostics, and several other archeologists, and maintain that both the former proceeded from Buddhism, at once the simplest and most satisfying of philosophies, and which resulted in one of the purest religions of the world. It is only a matter of chronology to decide which of these religions, differing but in external form, is the oldest, therefore the least adulterated. But even this bears but very indirectly, if at all, on the subject we treat of.
Already some time before our era, the adepts, except in India, had ceased to congregate in large communities; but whether among the Essenes, or the Neo-Platonists, or, again, among the innumerable struggling sects born but to die, the same doctrines, identical in substance and spirit, if not always in form, are encountered. By Buddhism, therefore, we mean that religion signifying literally the doctrine of wisdom, and which by many ages antedates the metaphysical philosophy of Siddhartha Sakyamuni.
After nineteen centuries of enforced eliminations from the canonical books of every sentence which might put the investigator on the true path, it has become very difficult to show to the satisfaction of exact science, that the “Pagan” worshippers of Adonis, their neighbors, the Nazarenes, and the Pythagorean Essenes, the healing Therapeutes, the Ebionites, and other sects, were all, with very slight differences, followers of the ancient theurgic Mysteries. And yet by analogy and a close study of the hidden sense of their rites and customs, we can trace their kinship.”
H. P. Blavatsky
The Mark Of God: Understanding Your "I AM Presence" 